Methods for periodic triggering of several beam-emitting elements are gaining greater and greater importance, for example in information technology. For example, arrays of luminescent diodes are used to expose photoconductive drums in printing equipment, said arrays being controlled by integrated circuits according to the image pattern to be represented. For example, TELEFUNKEN electronic GmbH has developed an LED module designated TPHM 8080 whose width equals the A4 format and which comprises a line of 2560 gallium-arsenide-phosphide luminescent diodes and 20 integrated circuits for driving the LEDs.
The image, resolved into a bit pattern, and which is to be reproduced by the LED line, is input into shift register ICs via an 8-bit parallel data flow. A pulse triggers the transfer of the bit pattern from the shift register to a data buffer memory. The various luminescent diodes are switched on by a further activation signal in accordance with the stored bit pattern.
In conventional control circuits, there is the limitation that a triggering pulse with the same amplitude and duration is provided for all individual diodes, so that the tolerance in the efficiencies between the individual elements had to be as narrow as possible for the emitted energy of all elements triggered to be substantially the same. This difficult requirement for efficiency scattering meant that the yield of suitable luminescent diodes for arrangement in rows was relatively low, with optimum uniformity of the energy emitted also not being obtainable due to unavoidable differences in the operating conditions for the individual components.